Flame retardant pht compositions

ABSTRACT

Hexahydrotriazine (HT) materials and hemiaminal (HA) materials derived from aromatic, aliphatic, and/or polyether diamines may he used as a platform for creating flame retardant materials. Various flame retardant material precursors may he incorporated into the HA and HT materials. Examples of flame retardant precursors may include organohalogen materials, organophosphorous materials, malamines, and dianiline compounds, among others. The flame retardant materials and precursors may he single molecule species, oligomers, and/or polymers (i.e., polyhexahydrotriazine, PHT, polyhemiaminal, PHA). The flame retardant materials may he made using an aromatic diamine, an aliphatic diamine, a polyether diamine, or a mixture thereof to react with an aldehyde (i.e. formaldehyde or paraformaldehyde). Such flame retardant material precursors will complex with the diamine monomers via a copolymerization reaction to form the flame retardant materials.

BACKGROUND

The present disclosure relates to flame retardant materials, and morespecifically, to the use of hexahydrotriazine and hemiaminal molecules,oligomers, and polymers derived from aromatic, aliphatic, and/orpolyether diamines to create flame retardant materials exhibiting flameretardant monomers covalently incorporated into a polymer matrix.

Flame retardant materials are commonly used for various applicationswhere exposure to high heat or power may be encountered. Examples ofindustries that commonly utilize flame retardant materials include theautomotive, aerospace, information technology, and telecommunicationsindustries, among others. These industries generally require flameretardant materials to prevent or significantly reduce the propensity ofa given material to burn to prevent catastrophic failures and costlyremediation.

Common flame retardant materials are generally limited in application tothe limitations associated with the polymers within which they areincorporated. These flame retardant materials also suffer from a lack ofrecyclability and often adversely affect the environment when thematerials are disposed of. For example, if a flame retardant materialcannot be effectively recycled, the material may be relegated todisposal in a landfill or other undesirable locale. The toxicity offlame retardant materials is often realized when the flame retardantleaches from the material into the surrounding environment. Theenvironmental and biological toxicity of these materials often harmflora and fauna exposed to the leached materials. In addition, the flameretardant material cannot be re-used if the materials suffer from beingnon-recyclable, thus, increasing the cost of manufacturing new flameretardant materials.

Thus, what is needed in the art are improved flame retardant materials.

SUMMARY

In one embodiment, a method of preparing a flame retardant material isprovided. The method includes providing an organic anhydride monomerfunctionalized with a flame retardant species and a diamine monomer. Theorganic anhydride monomer and the diamine monomer may be exposed to analdehyde material and a flame retardant polymeric compound comprising aPHA or PHT material matrix may be formed.

In another embodiment, a method of preparing a flame retardant materialis provided. The method includes providing an organic dianhydridemonomer functionalized with a flame retardant species and a diaminemonomer. The organic dianhydride monomer and the diamine monomer may beexposed to an aldehyde material and a flame retardant polymeric compoundcomprising a PHA or PHT material matrix may be formed.

In another embodiment, a method of preparing a flame retardant materialis provided. The method includes preparing a flame retardant materialcomprising brominating phthalic anhydride monomer and reacting thebrominated phthalic anhydride monomer with a diamine monomer. The flameretardant material may include an HA material having a plurality oftrivalent hemiaminal groups having the structure

and a plurality of bridging groups having the structure

y′ may be 2 or 3 K′ may be a divalent or trivalent radical comprising atleast one 6-carbon aromatic ring.

In yet another embodiment, a method of preparing a flame retardantmaterial is provided. The method includes preparing a flame retardantmaterial comprising brominating a phthalic anhydride monomer andreacting the brominated phthalic anhydride monomer with a diaminemonomer. The flame retardant material may include an HT material havinga plurality of trivalent hexahydrotriazine groups having the structure

and a plurality of divalent bridging groups having the structure

Each divalent bridging group may be bonded to two of the trivalenthexahydrotriazine groups and L′ may be a divalent linking group,

DETAILED DESCRIPTION

Hexahydrotriazine (HT) materials and hemiaminal (HA) materials derivedfrom aromatic, aliphatic, and/or polyether diamines may be used as aplatform for creating flame retardant materials. Various flame retardantmaterial precursors may be incorporated into the HA and HT materials.Examples of flame retardant precursors may include organohalogenmaterials, organophosphorous materials, melamines, and dianilinecompounds, among others. The flame retardant materials and precursorsmay be single molecule species, oligomers, and/or polymers (i.e.,polyhexahydrotriazine, PHT, polyhemiaminal, PHA). The flame retardantmaterials may be made using an aromatic diamine, an aliphatic diamine, apolyether diamine, or a mixture thereof to react with an aldehyde (i.e.formaldehyde or paraformaldehyde). Such flame retardant materialprecursors will complex with the diamine monomers via a copolymerizationreaction to form the flame retardant materials.

A PHT material suitable for forming a flame retardant material asdescribed herein is a molecule, oligomer, or polymer that has aplurality of trivalent hexahydrotriazine groups having the structure

and a plurality of divalent bridging groups of formula (2):

wherein is a divalent linking group selected from the group consistingof *—O—*, *—S—*, *—N(R′)—*, *—N(H)—*, *—R″—*, and combinations thereof,wherein R comprises at least 1 carbon and R″ comprises at least onecarbon, each starred bond of a given hexahydrotriazine group iscovalently linked to a respective one of the divalent bridging groups,and each starred bond of a given bridging group is linked to arespective one of the hexahydrotriazine groups. In one embodiment, R′and R″ are independently selected from the group consisting of methyl,ethyl, propyl, isopropyl, phenyl, and combinations thereof. Other L′groups include methylene (*—CH₂—*), isopropylidenyl (*—C(Me)₂-*), andfluorenylidenyl:

For PHT materials with bridging groups of formula (2), the HT may berepresented by formula (3):

wherein L′ is a divalent linking group selected from the groupconsisting of *—O—*, *—S—*, *—N(R′)—*, *—N(H)—* *—R″—*, and combinationsthereof, wherein R′ and R″ independently comprise at least 1 carbon.Each nitrogen having two starred wavy bonds in formula (3) is a portionof a different hexahydrotriazine group,

The PHT may also be represented by the notation of formula (4):

wherein x′ is moles, L′ is a divalent linking group selected from thegroup consisting of *—O—*, *—S—*, *—N(R′)—*, *—N(H)—*, *—R″—*, andcombinations thereof, wherein comprises at least 1 carbon and R″comprises at least one carbon. Each starred bond of a givenhexahydrotriazine group of formula (4) is covalently linked to arespective one of the bridging groups. Additionally, each starred bondof a given bridging group of formula (2) is covalently linked to arespective one of the hexahydrotriazine groups. Polymer molecules may becapped or terminated by a capping group in place of a bridging group informulas (3) and (4). Examples of capping groups include CH₃, hydrogenatoms, ether groups, thioether groups, and dimethyl amino groups.

The PHT or HT can be bound non-covalently to water and/or a solvent(e.g., by hydrogen bonds).

Exemplary divalent bridging groups include:

and combinations thereof.

A suitable PHT material may be made by forming a first mixturecomprising i) one or more monomers comprising two aromatic primary aminegroups, ii) an optional diluent monomer comprising one aromatic primaryamine group, iii) paraformaldehyde, formaldehyde, and/or anothersuitable aldehyde, and iv) a solvent, and heating the first mixture at atemperature of about 50° C. to about 300° C., preferably about 165° C.to about 280° C., thereby forming a second mixture comprising apolyhexahydrotriazine. The heating time at any of the above temperaturescan be for about 1 minute to about 24 hours. Diamine monomers suitablefor making such PHT materials may have the general structureH₂N—Ar-L′-Ar—N—H₂, where Ar denotes a benzene ring group and L′ isdefined as described above. Diluent monomers suitable for including inthe reaction are typically primary monoamines RNH₂, where the group Rbonded to nitrogen has a structure according to formula (5), formula(6), formula (7), and/or formula (8):

wherein W′ is a monovalent radical selected from the group consisting of*—N(R¹)(R²), *—OR³, —SR⁴, wherein R¹, R², R³, and R⁴ are independentmonovalent radicals comprising at least 1 carbon. The starred bonds informulas (5), (6), (7), and (8) denote bonds with the nitrogen atom ofthe primary amine monomer. Non-limiting exemplary diluent groupsinclude:

Diluent groups can be used singularly or in combination.

Non-limiting exemplary monomers comprising two primary aromatic aminegroups include 4,4′-oxydianiline (ODA), 4,4′-methylenedianiline (MDA),4,4′-(9-fluorenylidene)dianiline (FDA), p-phenylenediamine (PD),1,5-diaminonaphthalene (15DAN), 1,4-diaminonaphthalene (14DAN), andbenzidene, which have the following structures:

Non-limiting exemplary diluent monomers includeN,N-dimethyl-p-phenylenediamine (DPD), p-methoxyaniline (MOA),p-(methylthio)aniline (MTA), N,N-dimethyl-1,5-diaminonaphthalene(15DMN), N,N-dimethyl-1,4-diaminonaphthalene (14DMIN), andN,N-dimethylbenzidene (DMB), which have the following structures:

HT and HA material matricies may be used to incorporate flame retardantspecies to form flame retardant materials. It should be noted that manydiamines will react with aldehydes, such as formaldehyde, to form flameretardant materials by incorporating the flame retardant species intothe HT and/or HA polymer matrix. The incorporation of the flameretardant species into the HT and HA material matricies may beconsidered a copolymerization reaction between the diamine monomer andthe flame retardant species in certain embodiments.

A related material that may be used to create a flame retardant is ahemiaminal (HA) material. A polyhemiaminal (PHA) is a crosslinkedpolymer comprising a plurality of trivalent hemiaminal groups of formula(9):

covalently linked to ii) a plurality of bridging groups of formula (10):

wherein y′ is 2 or 3, and K′ is a divalent or trivalent radicalcomprising at least one 6-carbon aromatic ring. In formulas (9) and(10), starred bonds represent attachment points to other portions of thechemical structure. Each starred bond of a given hemiaminal group iscovalently linked to a respective one of the bridging groups.Additionally, each starred bond of a given bridging group is covalentlylinked to a respective one of the hemiaminal groups.

As an example, a polyhemiaminal can be represented by formula (11):

In this instance, each K′ is a trivalent radical (y=3) comprising atleast one 6-carbon aromatic ring. It should be understood that eachnitrogen having two starred wavy bonds in formula (11) is a portion of adifferent hemiaminal group.

The structure of formula (11) can also be represented using the notationof formula (12):

wherein x′ is moles and each bridging group K′ is a trivalent radical(y′=3 in formula (10)) comprising at least one 6-carbon aromatic ring.It should be understood that each starred nitrogen bond of a givenhemiaminal group of formula (12) is covalently linked to a respectiveone of the bridging groups K′. Additionally, each starred bond of agiven bridging group K′ of formula (12) is covalently linked to arespective one of the hemiaminal groups.

Non-limiting exemplary trivalent bridging groups for HA materialsinclude:

The bridging groups can be used singularly or in combination.

Polyhemiaminals composed of divalent bridging groups K′ can berepresented herein by formula (13):

wherein K′ is a divalent radical (y′=2 in formula (10)) comprising atleast one 6-carbon aromatic ring. Each nitrogen having two starred wavybonds in formula (13) is a portion of a different hemiaminal group.

More specific divalent bridging groups have the formula (14):

wherein L′ is a divalent linking group selected from the groupconsisting of *—O—*, *—S—*, *—N(R′)—*, *—N(H)—*, *—R″—*, andcombinations thereof, wherein R′ and R″ independently comprise at least1 carbon. In an embodiment, R′ and R″ are independently selected fromthe group consisting of methyl, ethyl, propyl, isopropyl, phenyl, andcombinations thereof. Other L′ groups include methylene (*—CH₂—*),isopropylidenyl (*—C(Me)₂-*), and fluorenylidenyl:

Polyhemiaminals composed of divalent bridging groups of formula (14) canbe represented herein by formula (15):

wherein L′ is a divalent linking group selected from the groupconsisting of *—O—*, *—S—*, *—N(R′)—*, *—N(H)—*, *—R″—*, andcombinations thereof, wherein R′ and R″ independently comprise at least1 carbon. Each nitrogen having two starred wavy bonds in formula (15) isa portion of a different hemiaminal group.

The polyhemiaminal of formula (15) can also be represented by thenotation of formula (16):

wherein x is moles, and L′ is a divalent linking group selected from thegroup consisting of *—O—*, *—S—*, *—N(R′)—*, *—N(H)—*, *—R″—*, andcombinations thereof, wherein R′ and R″ independently comprise at least1 carbon. Each starred nitrogen bond of a given hemiaminal group offormula (16) is covalently linked to a respective one of the bridginggroups. Additionally, each starred bond of a given bridging group offormula (16) is covalently linked to a respective one of the hemiaminalgroups.

The hemiaminal groups can be bound non-covalently to water and/or asolvent. A non-limiting example is a hemiaminal group that is hydrogenbonded to two water molecules as shown in formula (17):

In some embodiments, a hemiaminal material may form a covalent networkwith water molecules that may be a polyhemiaminal hydrate (PHH). A PHAmaterial of this form may be made, for example, by reaction ofpolyethylene glycol oligomers with paraformaldehyde. Such materials maybe organogels in some cases.

Typical HT and HA polymers and oligomers, and PHH materials, asdescribed herein may be disassembled in aqueous solutions, HT oligomersand polymers will disassemble into monomers and may dissolve in acidsolutions having pH less than about 3, such as less than about 2.5, forexample less than about 2. PHH materials may disassemble into monomersin neutral water. Such properties may be useful in removing flameretardant species from the polymer matrix. Various flame retardantspecies, which often exhibit varying degrees of environmental andbiological toxicity, may be recovered from the polymer matrix andproperly disposed of. The ability to disassemble the flame retardantmaterials allows the flame retardant species to be properly disposed ofand the HT or HA monomers to be reused. Thus, the flame retardantmaterials may be environmentally friendly, recyclable, and provide forcost effective reutilization of the flame retardant material precursors.

An HA, material suitable for use according to the methods describedherein may be made using the same groups of reactants as for the HTmaterials. The diluent monomers described above may also be used to makeHA materials. A method of preparing a polyhemiaminal (PHA) comprisingdivalent bridging groups comprises forming a first mixture comprising i)a monomer comprising two or more primary aromatic amine groups, ii) anoptional diluent monomer comprising one aromatic primary amine group,iii) paraformaldehyde, and iv) a solvent. The first mixture is thenpreferably heated at a temperature of about 20° C. to about 120° C. forabout 1 minute to about 24 hours, thereby forming a second mixturecomprising the PHA. In an embodiment, the monomer comprises two primaryaromatic amine groups. The mole ratio of paraformaldehyde: total molesof primary aromatic amine groups (e.g., diamine monomer plus optionalmonoamine monomer) may be about 1:1 to about 1.25:1, based on one moleor equivalent of paraformaldehyde equal to 30 grams. The solvent can beany suitable solvent. Exemplary solvents include dipolar aproticsolvents such as, for example, N-methyl-2-pyrrolidone (NMP),dimethylsulfoxide (DMSO), N,N-dimethylformamide (DMF),N,N-dimethylacetamide (DMA), Propylene carbonate (PC),N-cyclohexyl-2-pyrrolidone (CHP), N,N′-dimethylpropyleneurea (DMPU), andpropylene glycol methyl ether acetate (PGMEA).

A PHT material may be prepared from a PHA material. The PHT can beprepared by heating a solution comprising the PHA at a temperature of atleast 50° C., such as about 165° C. to about 280° C. or about 180° C. toabout 220° C., for example at about 200° C. for about 1 minute to about24 hours. Additionally, a mixed PHA/PHT copolymer may be made bypartially converting a PHA material to a PHT material. A combination oflow conversion temperature, for example about 150° C. to about 165° C.,and short conversion time, for example about 1 minute to about 10minutes, may be used to make a mixed PHA/PHT material.

An exemplary PHA material may be made by reaction of 4,4′-oxydianiline(ODA) with paraformaldehyde (PF). The product is a powder or solidplastic.

4,4′-Oxydianilin (ODA, 0.20 g, 1.0 mmol) and paraformaldehyde 0.15 g,5.0 mmol, 5 equivalents (eq.)) were weighed out into a 2-Dram vialinside a N₂-filled glovebox, N-methylpyrrolidone (NMP, 6.2 g, 6.0 mL,0.17 M) was added. The vial was capped but not sealed. The reactionmixture was removed from the glovebox, and heated in an oil bath at 50°C. for 24 hours (after approximately 0.75 hours, the polymer begins toprecipitate). The polyhemiaminal P-1 was precipitated in acetone orwater, filtered and collected to yield 0.22 g, >98% yield as a whitesolid.

A second exemplary PHA material may be prepared by reaction of4,4′-methylenedianiline (MDA) with PF:

ODA was substituted with 4,4′-methylenedianiline (MDA) and a mole ratioof MDA to PF of 1:5 was used. Solid yield of 0.15 g, 69%, was anamorphous, insoluble off-white powder.

A PHT material may be prepared by reaction of ODA and PF, as follows:

P-4, a polyhexahydrotriazine, was prepared by reaction of4,4′-oxydianiline (ODA) with paraformaldehyde (PF), ODA (0.20 g, 1.0mmol) and PF (0.15 g, 5.0 mmol, 2.5 eq.) were weighed out into a 2-Dramvial inside a N₂-filled glovebox. NMP (6.2 g, 6.0 mL, 0.17 M) was added.The reaction mixture was removed from the glovebox, and heated in an oilbath at 200° C. for 3 hours (after approximately 0.25 hours, the polymerbegins to gel in the NMP). The solution was allowed to cool to roomtemperature and the polymer was precipitated in 40 mL of acetone,allowed to soak for 12 hours, then filtered and dried in a vacuum ovenovernight and collected to yield 0.21 g, 95% yield of P-4 as anoff-white solid.

In one example, an organic anhydride functionalized with a flameretardant species, such as tetrabromophthalic anhydride, and a diaminemonomer, such as 4,4′-oxydianiline (ODA), may be reacted with analdehyde (i.e. formaldehyde or paraformaldehyde) and subsequently curedto enhance covalent cross-linking of the resulting flame retardantmaterial via condensation reactions. Solvents described above, such asdipolar aprotic solvents, may also be utilized to facilitate formationof the flame retardant materials. In one embodiment, the curing of theflame retardant material may be performed by heating the reactionmixture to between about 50° C. and about 280°C., such as greater thanabout 180° C., for example, about 200° C. An exemplary monofunctionalembodiment for forming the flame retardant materials is shown below.

In the monofunctional embodiment shown above, the tetrabromophthalicanhydride is added to the PHT polymerization ODA reacted withformaldehyde/paraformaldehyde). The copolymerization reaction results inthe ring opening of the anhydride to create an imide which is covalentlybound into the resulting flame retardant PHT material matrix. Thereaction product may be considered a polyimide/PHT copolymer in certainembodiments. Each nitrogen having two starred wavy bonds may be aportion of a different hexahydrotriazine group. In this embodiment, theflame retardant precursor may end terminate or cap the flame retardantmaterial. As such, the monofunctional embodiment may be useful forforming flame retardant material oligomers.

In another example, an organic dianhydride functionalized with a flameretardant species, such as bis(tribromophthalic)dianhydride, and adiamine monomer, such as 4,4′-oxydianiline (ODA), may be reacted with analdehyde (i.e. formaldehyde or paraformaldehyde) and subsequently curedto enhance covalent cross-linking of the resulting flame retardantmaterial via condensation reactions. Solvents described above, such asdipolar aprotic solvents, may also be utilized to facilitate formationof the flame retardant materials. In one embodiment, the curing of theflame retardant material may be performed by heating the reactionmixture to between about 50° C. and about 280° C., such as greater thanabout 180° C., for example, about 200° C. An exemplary bisfunctionalembodiment for forming the flame retardant materials is shown below.

In the bisfunctional embodiment shown above, thebis(tribromophthalic)dianhydride is added to the PHT polymerization(i.e. ODA reacted with formaldehyde/paraformaldehyde). As shown,biphthalic dianhydride may be brominated prior to performing thecopolymerization reaction. The reaction results in the ring opening ofthe anhydrides to create imides which are covalently bound into theresulting flame retardant PHT material matrix. The reaction product maybe considered a polyimide/PHT copolymer in certain embodiments. Eachnitrogen having two starred wavy bonds may be a portion of a differenthexahydrotriazine group. The functional group R may be a bridging group.By utilizing a dianhydride flame retardant monomer, additionalpolymerization and a higher degree of covalent cross-linking within thepolymer matrix may be achieved when compared to the monofunctionalembodiment.

With regard to the monofunctional and bisfunctional embodimentsdescribed above, bromination of the anhydride monomers may be performedby any convenient method. An exemplary bromination process is describedin U.S. Pat. No. 3,875,186, which is incorporated herein by reference inits entirety. Non-limiting examples of other flame retardant materialprecursors which may be incorporated into the PHT/PHA polymer matrix viaa copolymerization reaction include phosphates, melamines, and variousdianiline compounds. One example of a dianiline compound which may beincorporated into the PHT/PHA polymer matrix is4,4′-(Hexafluoroisopropylidene)bis(p-phenyleneoxy)dianiline.

In addition to the embodiments described above, other methods of formingflame retardant materials are contemplated. For example, in either themonofunctional or bisfunctionat embodiments, the anhydrides may bepre-reacted with bisaminos to create an amine that is covalently boundinto the PHT/PHA matrix similar to the ODA as described above. The aminemay be functionalized with a flame retardant species (i.e. bybromination or phosphorylation) prior to exposure to the aldehyde.

Further, it is contemplated that a diamine monomer may be functionalizedwith a flame retardant species and subsequently reacted to form aPHT/PHA flame retardant material. In this embodiment, anhydride monomersmay not be necessary to form the flame retardant materials.Alternatively, anhydride monomers may be copolymerized with a flameretardant functionalized diamine to form a polyimide and PHA/PHTcopolymer. In one example, a brominated diamine monomer may be utilized.An exemplary brominated diamine monomer is shown below. Although the Rgroup shown below is a brominated organic material, it is contemplatedthat any suitable halogenated organic material may be incorporated intothe diamine monomer.

The flame retardant materials and flame retardant material precursorsdescribed herein may be included in a composite material that may beused as a flame retardant material in any of the embodiments describedherein. Any desired blend material for a composite may be added to thereaction mixture of diamine and aldehyde prior to formation of areaction product. For example, reactants may be mixed at a non-reactingtemperature, for example less than about 50° C. for some embodiments,and a solid polymer material, for example a powder, a fiber aggregate,or a nanotube aggregate, may be added. The resulting combination may bemixed as the temperature is increased to form a reaction product. Anydesired polymer may form a composite material with an HA, HT, or PHHmaterial to provide selected properties. Carbon nanotubes may also forma composite with HA, HT, or PHH materials to provide additionalmechanical integrity in certain flame retardant material applications.

The flame retardant materials described herein may exhibit variousadvantageous properties including high modulus, solvent resistance, andenvironmental stress crack resistance, among others. However, the flameretardant materials may be chemically reverted to the monomers viatreatment with strong acid. Thus, the flame retardant materials may berecycled or reworked as desired. The recyclability of these flameretardant materials is especially suitable for environmentally friendlydisposal of the materials. In sum, the materials provide a covalentlybound flame retardant species within the polymer matrix and efficientand cost effective recyclability of the flame retardant materials. It iscontemplated that the flame retardant material may provide variousbenefits over current flame retardant materials and may be applicableacross various industries.

While the foregoing is directed to example embodiments of the presentdisclosure, other and further embodiments may be devised withoutdeparting from the basic scope thereof, and the scope thereof isdetermined by the claims that follow.

What is claimed is:
 1. A method of forming a flame retardant material,comprising: providing an organic anhydride monomer functionalized with aflame retardant species; providing a diamine monomer; exposing theorganic anhydride monomer and the diamine monomer to an aldehydematerial; and forming a flame retardant polymeric compound comprising aPHA or PHT material matrix.
 2. The method of claim 1, wherein theorganic anhydride monomer comprises phthalic anhydride.
 3. The method ofclaim 2, wherein the diamine monomer comprises ODA.
 4. The method ofclaim 1, wherein the PHA or PHT material comprises an aromatic bridginggroup.
 5. The method of claim 2, wherein the flame retardant speciescomprises a halogen based aromatic material.
 6. The method of claim 1,wherein the flame retardant species is selected from the groupconsisting of halogen based materials, phosphate materials, melaminematerials, and dianiline materials.
 7. The method of claim 1, whereinthe organic anhydride monomer functionalized with a flame retardantspecies comprises tetrabromophthalic anhydride.
 8. The method of claim1, wherein the flame retardant polymeric compound is formed by a processcomprising: forming a mixture comprising one or more monomers comprisingtwo aromatic primary amine groups having the general structureH₂N—Ar-L′-Ar—N—H₂, wherein Ar denotes a benzene ring group and L is adivalent linking group, and a solvent; and heating the mixture at atemperature of about 50° C. to about 280° C. for about 1 minute to about24 hours.
 9. The method of claim 1, wherein the exposing the organicanhydride monomer and the diamine monomer to an aldehyde materialcomprises forming an imide moiety which is covalently bound to the PHAor PHT material matrix.
 10. A method of forming a flame retardantmaterial, comprising: providing an organic dianhydride monomerfunctionalized with a flame retardant species; providing a diaminemonomer; exposing the organic dianhydride monomer and the diaminemonomer to an aldehyde material; and forming a flame retardant polymericcompound comprising a PHA or PHT material matrix.
 11. The method ofclaim 10, wherein the organic anhydride monomer comprises biphthalicdianhydride.
 12. The method of claim 11, wherein the diamine monomercomprises ODA.
 13. The method of claim 10, wherein the PHA or PHTmaterial comprises an aromatic bridging group.
 14. The method of claim11, wherein the flame retardant species comprises a halogen basedaromatic material.
 15. The method of claim 10, wherein the flameretardant species is selected from the group consisting of halogen basedmaterials, phosphate materials, melamine materials, and dianilinematerials.
 16. The method of claim 10, wherein the organic anhydridemonomer functionalized with a flame retardant species comprisesbis(tribromophthalic)dianhydride.
 17. The method of claim 10, whereinthe flame retardant polymeric compound is formed by a processcomprising: forming a mixture comprising one or more monomers comprisingtwo aromatic (primly amine groups having the general structureH₂N—Ar-L′-Ar—N—H₂, wherein Ar denotes a benzene ring group and L′ is adivalent linking group, and a solvent; and heating the mixture at atemperature of about 50° C. to about 280° C. for about 1 minute to about24 hours.
 18. The method of claim 1, wherein the exposing the organicanhydride monomer and the diamine monomer to an aldehyde materialcomprises forming an imide moiety which is covalently bound to the PHAor PHT material matrix.
 19. A method of forming a flame retardantmaterial, comprising: preparing a flame retardant material comprisingbrominating a phthalic anhydride monomer and reacting the brominatedphthalic anhydride monomer with a diamine monomer, wherein the flameretardant material comprises an HA material having a plurality oftrivalent hemiaminal groups having the structure

and a plurality of bridging groups having the structure

wherein y′ is 2 or 3, and K′ is a divalent or trivalent radicalcomprising at least one 6-carbon aromatic ring.
 20. A method of forminga flame retardant material, comprising: preparing a flame retardantmaterial comprising brominating a phthalic anhydride monomer andreacting the brominated phthalic anhydride monomer with a diaminemonomer, wherein the flame retardant material comprises an HT materialhaving a plurality of trivalent hexahydrotriazine groups having thestructure

and a plurality of divalent bridging groups having the structure

each divalent bridging group bonded to two of the trivalenthexahydrotriazine groups, wherein L′ is a divalent linking group.